I talked to a VA landowner yesterday who owns a cave (unknown to him) that is consistently clogged with debris. The small entrance is in a sinkhole that takes water from the hillside almost year-round. He cleans the junk out of there from time to time so that the water will drain better. The cave is described as a crawl to a 90' pit with 400' of large stream passage below. Because of its situation, I am very interested in this cave as a potential part of a much larger and so far undiscovered drainage. While the owner doesn't believe that there is a pit in his sinkhole, I have definitely identified it in person as the right location. He is willing to let me dig the thing open again, and check it out. We talked on the phone about ways to keep the entrance from getting clogged while still allowing good drainage. I don't really have any experience with this sort of thing and wonder if anyone has any ideas. Ideally, we could keep the entrance open, the water flowing, and the inevitable debris pile manageable. Any tips?

You may be able to construct and anchor some sort of grate in the flow path to catch debris before it goes in the entrance and then periodically clean it out. Could be metal, wood, webbing, etc. and to reduce chance of damming, could use more than one grate with a coarser one first to catch big stuff and a finer one or more behind to catch smaller stuff.

I think a comination of the ideas from boreholio and Chads93GT might work best and be the cheapest way to solve the problem. But rather than constructing grates of varying opening sizes and considerable expense, I suggest using a short section of fence at two or three or even four intervals one after the other. A strong section of fence to catch large debris before it goes down into the sink, followed by a slightly finer section of fence and so on. Sections as little as 10 to 20 feet wide may be enough to do the trick, depending on the size of the stream going into the sink. Each section of fence should also be at least 10 to 20 feet apart from the other section to facilitate access for cleaning out debris. And as Chads93GT suggested, cleaning up the watershed upstream might help reduce the amount of debris coming toward the sink and fences. Fencing is relatively cheap and farmers are familiar with installing it. Welded wire fencing is also available in many different styles with openings of varying sizes. If the ground is rocky, metal fence posts might work best and can be set with concrete if necessary.

Thanks! The watershed is a steep, large, wooded hillside, so I don't know that much can be gained by fiddling with that. I am, however, a bona-fide fence expert and have been considering various such solutions. I wonder if there is any way to incorporate a culvert, the guy says he has a bit lying around. If a culvert was placed through the fence, can you think of a way to direct crap around the opening while allowing water? I would like to set the barrier well up out of the sink so that it's easier for the owner to clean the mess up. While I'm sure I can figure something out, this can't be an isolated problem and some of you have surely faced similar. I would like to fix it up as nicely as possible for the owner.

How about a fence or series of fences with a French drain beneath it/them. Allows the water to flow beneath the fence without the debris following. A culvert might become filled with debris, where as the French drain would typically allow drainage unless water flow was so rapid that leaching subsurface wasn't happening. I had to do this once on a trail along a floodplain where boardwalks lined the ravine along the sides of the floodplain. This kept the water draining but kept the debis off the sides of the boardwalk.

GroundquestMSA wrote:What kind of volume can a French drain handle? Will a layer of leaves and sticks atop it destroy its effectiveness?

The largest flexible French drain pipe I've seen is 6". 3" to 4" is common. A picture would be helpful, but I'm guessing a French drain will only handle light rain fall.

How about taking the biggest culvert you can fit down the entrance hole, preferably 24" to 36", and leave about a foot of it sticking up above grade. When installing, you wrap the culvert in perforated drain board so that the water drains down the outside of it, thus slowly draining the area right around the culvert. I'd still use the fence idea to catch the bigger stuff, but for really large flows, you will put a screen over the culvert entrance to catch anything that gets past the fences. Basically large flows will go down the culvert and the rest will settle out and drain around the outside of it. Make sure to wrap the drain board material with landscape fabric if it doasn't come with it preinstalled.

caverdan wrote:How about taking the biggest culvert you can fit down the entrance hole, preferably 24" to 36"...

The entrance Is probably one foot high and two-and-a-half or three wide. So it clogs easily, especially with the regular flow. It would take a lot of blasting at the entrance crawl to make any significant difference, and I'm not willing to get into that sort of destruction. The simpler the better, I don't want to start some sort of massive construction site. I hope to show up with a few materials in my van and get the job done in a few hours. Remember I live 6 hours away from this cave, so I don't want to make a career of building a trash gate. Thanks for the ideas. I'll let you know if it works out.

just pull all of the big sticks out of the valleys leading into the entrance and by that I mean the "ditch" where the water flows. Sticks = clogs. leaf clogs aren't a big deal and rot away quick. Logs on the other hand don't. But 6 hours away........wow......id chalk that up as a who cares ;) Good luck.

Chads93GT wrote:But 6 hours away........wow......id chalk that up as a who cares ;) Good luck.

I just wanted to do something useful for the old man. He's letting me root around his place, and he says he's been struggling to keep up with things like cleaning out the sink. He doesn't want a rotting pile of mosquito-filled sludge or a pond of water next to his house.